Migratory native fish will soon find it easier to find their way along the rivers and streams of the Ōhiwa region after careful study of the culverts and bridges in the watershed.
The Bay of Plenty Regional Council is leading the ambitious project to check all the culverts in the Ōhiwa Harbor catchment area to see if they allow fish to swim freely or not, on behalf of the seven partner organizations of the Ōhiwa port strategy.
The Area Council’s land manager, Tim Senior, explains that many of our native fish species migrate between fresh and salt water during their life cycle and it was important that the culverts and other man-made structures allow fish access to spawning and rearing habitat as well as food sources.
These fish include inanga, koaro, three species of kōkopu (white bait), and tuna (long and short eel).
“Essentially, certain man-made structures, like culverts, if not properly constructed or maintained, can prevent fish from returning to their spawning sites to reproduce or leaving their spawning site to mature.
“This leads to a decrease in the population. For a healthy ecosystem and increased biodiversity, we need to ensure that these fish species can complete their migration pattern.
Mikayla Binney, a student at the University of Lincoln, worked as a summer assistant to the Regional Council during summer vacation.
Mikayla Binney, Summer Assistant for the Bay of Plenty Regional Council, checks culverts on an Ohiwa-area farm. This allows good fish passage and does not need to be sanitized. Photo: BOPRC.
As part of her work, she visited culverts previously identified on aerial photographs to check if they allow fish migration.
This includes measuring the diameter of the culvert, if it is perched too far above the stream bed or if it has buried itself in the stream bed.
Mikayla also notes all the species of fish she sees during her inspection.
Observations made during these visits are then uploaded onto a map so that Regional Council staff can easily see where fish may be getting stuck and which culverts may need improvement.
Tim says the next step over the next year will be to retrofit culverts as needed with fish passage features. This is usually a fairly straightforward process and will be done at no cost to property owners.
“We would like to thank the landowners for their help in this project and their hospitality on their farms.
“We are grateful to see locals supporting this work to improve the conditions for our often unnoticed and forgotten but unique migratory fish.”
An example of a culvert perched too high and which does not allow the passage of fish. Photo: BOPRC.